This protocol is a modification of #327 to study metabolic acidosis in dialysis patients. The modified protocol will enhance patient recruitment. It will also allow the investigators to determine whether metabolic acidosis stimulates protein catabolism in hemodialysis patients, and whether this is due, at least, in part to activation of genes responsible for protein and amino acid degradation in skeletal muscle. The revised protocol has received IRB and GCRC approval, and recruitment has begun.